Regarding birthdays, I understand what Rattigan means to an extent. Being born is an accident of circumstances for us (or fate, if you believe in that) - not something we put effort into. Whereas, making a marriage last another year requires effort from both parties.
Marriage is supposed to be until death parts you from one another. So every year that both husband and wife live, then they are going to remain married. Therefore, if a married couple celebrates their wedding anniversary each year, what they are really celebrating is that neither one of them died during that year. Where's the effort in that?
If you claim that regardless of marriage supposing to be until death, that many get a divorce because they don't get along and have to put effort into making their marriage last year to year and therefore should celebrate each year that they make it, then I guess that can apply to any relationship friend or family member. You should celebrate every year with whomever you stay friends with and with whatever family you continue to have a relationship with. Doesn't it take effort to keep relationships with all people, not just spouses? Either celebrate yearly each and every relationship you have with a person or realized that it is foolish to think there is reason to celebrate a wedding date.
Again, the question I am waiting to hear an answer to from Rattigan is why do JWs have baby showers? And how does the reason for doing so not apply to year one and two, etc.. of that same child that a baby shower was given for?